1. Field of the Invention
The present invention relates to valves used to control the flow of a fluid, such as water, in a conduit. Valves according to the invention have broad utility but are particularly useful in underground sprinkler and irrigation systems, where low part fabrication and assembly costs must be balanced against the need for designs which provide high reliability and durability. The invention also relates to an improved valve diaphragm design, and to the design of an improved self-cleaning filter used in such valves to help prevent malfunctions due to contamination by dirt particles in the water.
2. Relevant Art
Flow control valves used in such applications generally employ liquid-pressure activated diaphragms to control opening and closing by the pressure of the liquid being transported, and can be operated manually or by a pilot mechanism actuated hydraulically or by a low power solenoid. Representative flow control valves are shown in U.S. Pat. Nos. 3,439,895; 4,301,992; 4,336,918; and 4,508,136. U.S. Pat. No. 5,645,264, which is incorporated herein by reference as if fully disclosed, describes a through-flow, diaphragm operated valve which has a circular tilted valve seat and a matching spherical valve plug. These patents, in turn, refer to other patents and valve assemblies.